1. Field of the Invention
The present invention relates to a surface mount antenna which can be mounted on a circuit board of a radio communication apparatus, a method of manufacturing the surface mount antenna, as well as a radio communication apparatus equipped with such a surface mount antenna.
2. Description of the Related Art
An antenna (surface mount antenna) which can be mounted on a circuit board of a radio communication apparatus includes a chip-like substrate (for example, a dielectric substrate), and a radiation electrode disposed on the chip-like substrate for transmitting and receiving communication signals (electromagnetic wave). Such a surface mount antenna may be manufactured by performing a plating treatment on the chip-like substrate so as to form an electrode, followed by an etching treatment in which the electrode is etched so as to have a predetermined shape, thereby obtaining a desired radiation electrode. Alternatively, an amount of paste material for forming a thick-film electrode is printed on to the surface of the chip-like substrate so as to form an electrode having a predetermined shape, followed by drying and sintering the printed paste material, thereby obtaining a desired surface mount antenna.
However, a surface mount antenna is usually small in size. Conventionally, since a surface mount antenna is produced individually by forming a radiation electrode on each small chip-like substrate, it is difficult to ensure high production efficiency, hence making it difficult to produce the surface mount antenna at a low cost.
Moreover, since it is extremely difficult to produce a great number of dielectric substrates having sizes and dielectric constants that are exactly the same as one another, it is extremely difficult for many radiation electrodes to have exactly the same resonance frequency. In order to inhibit such non-uniformity among the resonance frequencies of many radiation electrodes, it might be necessary to adjust, with very high precision, the shape of the radiation electrodes by taking into account the sizes and dielectric constants of many radiation electrodes. However, since each radiation electrode is extremely small in size, it is extremely difficult to perform such an adjustment of the shape of each radiation electrode.
Moreover, if the resonance frequency of the radiation electrode of each surface mount antenna is to be changed, it will be necessary to newly design the shape and size of each radiation electrode, as well as to newly design the size of each dielectric substrate, hence requiring a considerable amount of time and labor.
In order to overcome the problems described above, preferred embodiments of the present invention provide an improved surface mount antenna which permits a high production efficiency in its manufacturing process and allows an easy adjustment of the resonance frequency of the radiation electrode of each surface mount antenna, as well as an easy change in designing such an antenna. In addition, preferred embodiments of the present invention provide a method for manufacturing such an improved surface mount antenna, as well as a radio communication apparatus equipped with such an improved surface mount antenna.
According to a first preferred embodiment of the present invention, a surface mount antenna includes a substantially rectangular substrate and a radiation electrode disposed on the substantially rectangular substrate for performing an antenna function. In detail, the radiation electrode is disposed on four continuously connected surfaces including a top end surface, a bottom surface, and two shorter edge surfaces of the substrate, thereby forming a configuration essentially surrounding an outer circumference of the substrate. Specifically, a slit is formed in a direction intersecting an outer circumferential direction of the substrate and extends across the whole width of the radiation electrode. In particular, at least one of two electrode ends located close to each other with the slit interposed therebetween is cut for adjusting the resonance frequency of the radiation electrode.
According to a second preferred embodiment of the present invention, a method of manufacturing a surface mount antenna includes the steps of forming an electrode to entirely cover the top and bottom surfaces as well as two mutually opposite shorter edge surfaces of a dielectric substrate, forming a slit on the electrode disposed on the surface of the dielectric substrate, the slit being formed by cutting with a dicer and arranged in a direction intersecting a direction connecting the two shorter edge surfaces, cutting the dielectric substrate into a plurality of portions, using a dicer which cuts along the direction connecting the two end surfaces, and producing a plurality of surface mount antennas each including a substantially rectangular substrate and a radiation electrode formed to essentially surround the substantially rectangular substrate. In particular, when the dicer is used to cut the slit so that the slit is formed on the electrode attached to the surface of the dielectric substrate, the slit is formed at a position and having a width both corresponding to a predetermined resonance frequency of the radiation electrode of a surface mount antenna.
According to a third preferred embodiment of the present invention, another method of manufacturing a surface mount antenna includes the steps of forming an electrode to entirely cover the top and bottom surfaces as well as two mutually opposite shorter edge surfaces of a dielectric substrate, forming on the surface of the dielectric substrate, an electrode having a slit formed in a direction intersecting a direction connecting the two shorter edge surfaces, cutting the dielectric substrate into a plurality of portions, using a dicer which cuts along the direction connecting the two end surfaces, and producing a plurality of surface mount antennas each including a substantially rectangular substrate and a radiation electrode formed to essentially surround the substantially rectangular substrate. In particular, before the dielectric substrate is cut by a dicer into a plurality of portions, at least one of two electrode ends located close to each other with the slit interposed therebetween is cut by the dicer, so as to adjust the resonance frequency of the radiation electrode of each surface mount antenna to a predetermined resonance frequency.
According to another preferred embodiment of the present invention, either a plating treatment or a thick-film electrode formation method is preferably used to form an electrode on the dielectric substrate.
According to a further preferred embodiment of the present invention, a radio communication apparatus includes a surface mount antenna formed according to various preferred embodiments described above.
According to preferred embodiments of the present invention, the radiation electrode of each surface mount antenna is formed over four continuously connected surfaces including a top surface, a bottom surface and two shorter edge surfaces of a dielectric substrate, thereby forming a configuration essentially surrounding an outer circumference of the substrate. Further, a slit is provided on the radiation electrode, arranged in a direction intersecting the circumferential direction of the substrate and extending across the whole width of the radiation electrode. Moreover, an open end is formed. In addition, since the slit position and the slit width are variable, it is possible to change an electric length extending from a feeding section that is predetermined in the radiation electrode to the open end (an electrode end which is an edge of the slit), thereby making it possible to change the resonance frequency of the radiation electrode.
In preferred embodiments of the present invention, since the resonance frequency of the radiation electrode can be easily adjusted by using a dicer to change the slit position and the slit width, it is possible to easily and quickly perform any design change desired. Further, since the radiation electrode has an extremely simple shape, it can be easily manufactured. For example, the above-described surface mount antenna may be easily manufactured by using the above-described manufacturing method. More specifically, with the use of the method of preferred embodiments of the present invention, it is possible to produce a plurality of surface mount antennas in only one operation, thereby greatly reducing the production cost. Further, since a dicer can be used to process (with a high precision) an electrode, it is easy for the radiation electrode to obtain a predetermined resonance frequency by adjusting the slit position and the slit width.
Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.